Revealing mistake: When the UFO makes the huge flash that knocks everyone in the cemetery down, one of the police officers kicks a tombstone as he falls and it wobbles back and forth. (00:13:35)
Revealing mistake: When the flying saucers leave the planet, you can see their shadows on the fake planet's surface.
Revealing mistake: Vampira flinches when Inspector Clay fires at her even though she's a zombie. (00:15:05)
Revealing mistake: The "Old man-ghoul" changes appearances drastically throughout the entire movie. In some scenes, it is Bela Lugosi in vampire cape, in others it is the famous "double" who is a head taller than Lugosi, a lot thinner and has a different hairstyle. He covers his face with his cape, but this does not help a lot...
Revealing mistake: During Criswell's opening and closing narrations it is painfully obvious that he is reading from a cue card. (00:00:30 - 01:16:50)
Revealing mistake: After Clay finally has been killed, you can still see him breathing, and even blinking his eyes.
Revealing mistake: Jeff's wife is named Paula and is played Mona McKinnon, but when he is talking to her about having to hush up his UFO sighting, he calls her Mona. (00:12:50)